'Wrong' error msg in code editor

I often get this err msg in the code editor:
which not always means that the script wasn’t saved ??
(quite cumbersome)

If the editor tab has not been used for a while, it can disconnect from the server and leads to the error message you have seen where it doesn’t save. I usually do a select all -> copy -> refresh browser tab -> paste -> save, when that happens.

ok, me to - but nice with an explanation